The invention relates to a method and to a corresponding device for positioning a vehicle over the base unit of an inductive charging system.
Vehicles with an electric drive typically have a battery in which electrical energy for operating an electric machine of the vehicle can be stored. The battery of the vehicle can be charged with electrical energy from a power supply grid. For this purpose, the battery is coupled to the power supply grid in order to transmit the electrical energy from the power supply and into the battery of the vehicle. The coupling can be effected in a wire-bound fashion (via a charging cable) and/or in a wireless fashion (using an inductive coupling between a charging station and the vehicle).
An approach for automatic cableless inductive charging of the battery of the vehicle includes transmitting electrical energy to the battery from the floor to the underfloor of the vehicle by way of magnetic induction across the underfloor clearance 120. This is illustrated, for example, in FIG. 1. In particular, FIG. 1 shows a vehicle 100 with a storage unit 103 for electrical energy (e.g. with a chargeable battery 103). The vehicle 100 has what is referred to as a secondary coil in the underfloor of the vehicle, wherein the secondary coil is connected to the storage unit 103 via an impedance adaptor (not shown) and a rectifier 101. The secondary coil is typically part of what is referred to as a “wireless power transfer” (WPT) vehicle unit 102.
The secondary coil of the WPT vehicle unit 102 can be positioned above a primary coil, wherein the primary coil is mounted e.g. on the floor of a garage. The primary coil is typically part of what is referred to as a WPT base unit 111. The primary coil is connected to a power supply 110 (in this document also referred to as a charging unit 110). The power supply 110 can be a radiofrequency generator which generates an AC (Alternating Current) in the primary coil of the WPT base unit 111, as a result of which a magnetic field is induced. This magnetic field is also referred to in this document as an electromagnetic charging field. The electromagnetic charging field can have a predefined charging field frequency range. The charging field frequency range can be in the LF (Low Frequency) range, e.g. 80-90 kHz (in particular 85 kHz) or approximately 145 kHz.
Given sufficient magnetic coupling between the primary coil of the WPT base unit 111 and the secondary coil of the WPT vehicle unit 102 across the underfloor clearance 120, the magnetic field induces a corresponding voltage and therefore also a current in the secondary coil. The induced current in the secondary coil of the WPT vehicle unit 102 is rectified by the rectifier 101 and stored in the storage unit 103 (e.g. in the battery). It is therefore possible to transmit energy in a cableless fashion from the power supply 110 to the energy storage unit 103 of the vehicle 100. The charging process can be controlled in the vehicle 100 by way of a charging control unit 105 (also referred to as a WPT control unit 105). The charging control unit 105 can for this purpose be configured to communicate, e.g. in a wireless fashion, the charging unit 110 (e.g. with a wall box) or with the WPT base unit 111.
For an effective transfer of energy by means of the electromagnetic charging field it is typically necessary for the WPT vehicle unit 102 to be positioned relatively precisely over the WPT base unit 111. This positioning can be assisted by determining the position of the vehicle 100 relative to the WPT base unit 111.
The present document is therefore concerned with the technical task of determining, in an efficient and precise fashion, a position of the vehicle 100 relative to the WPT base unit 111 of an inductive charging system. The intention has been here to enable the determination of the position for vehicles 100 from a multiplicity of different manufacturers. In other words, the determination of the position should be independent of the manufacturer and/or applicable to all manufacturers.
According to one aspect of the invention, a charging station for wirelessly transmitting electrical energy to a vehicle (e.g. to a vehicle with an electric drive) is described. The vehicle may be, in particular, a land vehicle, e.g. a passenger car, a truck or a motorcycle. The charging station includes a base unit which is configured to generate an electromagnetic charging field for transmitting electrical energy to the vehicle. The base unit can include, in particular, a primary coil which is configured to generate the electromagnetic charging field.
The charging station also includes a receiver unit which is configured to receive a request signal from a transmitter unit of a vehicle. The request signal can comprise, in particular, a request signal of a keyless access function and/or of a keyless engine start function of a vehicle. The receiver unit can be arranged on or in the base unit. Alternatively or additionally, the receiver unit can be arranged on a charging unit (e.g. on a wall box) of the charging station.
The receiver unit can be configured in such a way that a request signal can be received from any of a plurality of different frequency ranges. In other words, the receiver unit can be configured to receive request signals which each lie in one of a plurality of different frequency ranges.
The receiver unit is also configured to detect a signal strength of the received request signal. The signal strength of the received request signal can be used to determine the position of the vehicle which has emitted the request signal, relative to the charging station and, in particular, relative to the base unit.
The fact that the receiver unit can receive request signals in a plurality of different frequency ranges permits vehicles from different manufacturers to be positioned. The plurality of different frequency ranges can include, for example, one or more of the following frequency ranges: a frequency range around 21 kHz; a frequency range around 80 kHz; a frequency range around 125 kHz; and/or a frequency range around 132 kHz. The individual frequency ranges of the request signals can be delimited substantially from one another. In other words, the frequency ranges of the request signals can be such that request signals do not substantially disrupt one another in different frequency ranges.
As stated above, the receiver unit can be arranged on or in the base unit. In particular, the receiver unit can be secured (in contrast to a key for an access function) at a fixed position and/or can have a fixed orientation in the space. The receiver unit can then be configured to evaluate the individual direction components of a reception field (e.g. an X component, Y component and Z component) individually for the sake of better resolution. As a result, the quality of the reception of the one or more request signals can be increased.
In order to detect the signal strength, the receiver unit can be configured to receive a signal (e.g. an analog electrical signal) which includes the request signal. The receiver unit can also be configured to detect the frequency range of the request signal as a frequency range from the plurality of different frequency ranges. For example, an information item of the frequency range of the request signal can be transmitted from the vehicle which has emitted the request signal to the charging station. Furthermore, the receiver unit can be configured to condition and/or process the received signal as a function of the detected frequency range of the request signal. In particular, a frequency component of the received signal which lies in the frequency range of the request signal can be isolated in order to detect the conditioned signal. The signal strength of the request signal can then be detected on the basis of the conditioned signal. As a result, precise detection of the signal strength of the request signal is made possible, which in turn permits precise determination of the position of the vehicle which has emitted the request signal.
The receiver unit can include a receiver unit which is configured to convert an electromagnetic field (which includes the request signal) into an analog electrical signal (e.g. into the received signal). Furthermore, the receiver unit can include a signal conditioning unit which is configured to damp the analog electrical signal in a charging field frequency range of the electromagnetic charging field relative to the analog electrical signal in one or more of the plurality of different frequency ranges. In other words, the signal conditioning unit can be configured to reduce the signal strength of that component of the received signal which is based on an electromagnetic charging field relative to other signal components. As a result, inaccuracies during the detection of the signal strength of the request signal, which originate from an electromagnetic charging field, can be reduced or avoided. Consequently, the accuracy of the determination of the position of the vehicle increases in this way.
As stated above, the receiver unit can be configured to detect the frequency range of the request signal from the plurality of different frequency ranges. Furthermore, the receiver unit can be configured to adapt the signal conditioning unit to the frequency range of the request signal. In particular, the signal conditioning unit can be adapted in such away that a component of the received signal which is based on the request signal is emphasized relative to other components.
Alternatively, the receiver unit can be configured to damp the analog electrical signal in the charging field frequency range relative to the analog electrical signal in all of the plurality of different frequency ranges, and to damp the analog electrical signal in the plurality of different frequency ranges with a predefined damping or less. In other words, the signal conditioning unit can be configured in a static fashion and can emphasize the signal components of all the possible frequency ranges of the plurality of different frequency ranges relative to the signal component in the charging field frequency range.
The receiver unit can also include an analog-to-digital converter which is configured to convert a signal derived from the analog electrical signal into a digital signal. Furthermore, the receiver unit can include a filter unit which is configured to raise the digital signal in one of the plurality of different frequency ranges relative to the digital signal into the other of the plurality of different frequency ranges. In particular, the component of the digital signal which lies in the frequency range of the request signal can be isolated and/or emphasized.
Furthermore, the receiver unit can include a detection unit which is configured to detect a signal strength of the signal at the output of the filter unit. The signal at the output of the filter unit can primarily include components of the received request signal. Consequently, the signal strength of the request signal can be determined in a precise fashion.
The filter unit can include a digital filter. The digital filter can be sequentially adapted to the plurality of different frequency ranges. It is therefore possible to detect in a sequential fashion whether and, if appropriate in which frequency range, a request signal is received. The charging station can therefore determine (without information from a vehicle) which frequency range the vehicle emits request signals in.
The request signal may have been transmitted by a transmitter unit of the vehicle to which electrical energy is to be transmitted via the base unit. The receiver unit can then be configured to make available the detected signal strength in order to detect a position of the vehicle relative to the base unit. In particular, the detected signal strength can be transmitted to the vehicle in order to permit the vehicle to carry out positioning above the base unit.
The charging station can also be configured to cause the base unit to reduce a field strength of the electromagnetic charging field if the reception of a request signal has been detected by means of the receiver unit. It is therefore possible to ensure that a positioning process and/or a keyless access function is not disrupted by an electromagnetic charging field.
According to a further aspect, a method for determining the position of a vehicle relative to a charging station is described. The method includes transmitting a request signal from the vehicle. In this context, the request signal can lie in any of a plurality of different frequency ranges. The method also includes receiving a signal at the charging station, wherein the received signal includes the request signal. The method also includes detecting the frequency range of the request signal at the charging station as a frequency range from the plurality of different frequency ranges. The received signal is then conditioned as a function of the detected frequency range of the request signal, and the signal strength of the request signal is detected on the basis of the conditioned signal. The position of the vehicle relative to the charging station can be determined on the basis of the detected signal strength.
According to a further aspect, a software (SW) program is described. The SW program can be configured to be run on a processor (e.g. on a control unit) and to thereby carry out the method described in this document.
According to a further aspect, a storage medium is described. The storage medium can store a SW program which is configured to be run on a processor and thereby to carry out the method described in this document.
It is to be noted that the methods, devices and systems described in this document can be used both alone and in combination with other methods, devices and systems described in this document. Furthermore, any aspects of the method, device and systems which are described in this document can be combined with one another in a variety of ways. In particular, the features of the claims can be combined with one another in a variety of ways.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.